The invention relates generally to an open-end friction spinning machine with a plurality of adjacently arranged spinning units each containing means for forming a yarn formation zone for the spinning of yarn, a feeding and opening device for supplying individual fibers to the yarn formation zone, a suction device for holding the fibers and the yarn being produced in the yarn formation zone and a withdrawal device for withdrawing the yarn from the yarn formation zone. Additionally provided are a winding or spooling device for collecting the spun yarn on a spool and a movable maintenance device capable of engagement with a spinning unit requiring service. This maintenance device includes devices for taking-up a broken yarn end at the respective spinning unit, devices for returning the yarn end to the spinning unit, devices for controlling the supply of fibers to the friction zone, devices for controlling the withdrawal of start-spun yarn out of the yarn formation zone, and devices for controlling the resumption of taking-up the piecing yarn onto the spool.
An open-end friction spinning machine is disclosed in DE-OS No. 33 25 928 which includes a plurality of adjacently arranged spinning units and a movable maintenance device for conducting a start-spinning process following a yarn break. The movable maintenance device is equipped with devices for detecting the broken yarn end and for returning the same into the spinning unit. Thereby the spinning unit is opened first to expose the area of the wedge-shaped gap which serves as the yarn formation zone. The broken yarn end is then introduced into a component part pivoted open and containing the fiber feed channel. The introduction of the yarn end is supported by a compressed air nozzle or jet which is part of the movable maintenance device. Subsequent thereto, the component part is pivoted back into the operational position, thereby closing the spinning unit. A vacuum is produced by means of a suction pipe in the area of the yarn formation zone which consists of the wedge-shaped gap formed by two rollers. This vacuum draws the yarn end further into the spinning unit and thereby into the suction pipe. The suction pipe is attached to the spinning unit. This suction pipe is connectable to a vacuum supply line forming part of the movable maintenance device.
An objective of the present invention is the provision of an open-end friction spinning machine with a movable maintenance device in such a manner that the return of the broken yarn end is simplified and functionality of the unit is improved.
These and other objectives of the present invention are achieved by providing an air current device controlled by the maintenance device for producing an air current extending over the yarn formation zone of a spinning unit. The air current means are suitable for returning a yarn end against the normal yarn withdrawal direction, and include at least one compressed air nozzle. The blowing direction of the nozzle is directed against the normal yarn withdrawal direction essentially in the longitudinal direction of the yarn formation zone according to a preferred embodiment.
This arrangement makes the return of the yarn end in a closed spinning unit possible. Additionally, a very effective transport air current is produced by means of the compressed air nozzle for the return of the yarn end.
In a further development of certain preferred embodiments of the invention, each spinning unit is provided with a yarn withdrawal pipe designed as an extension of the yarn formation zone which for producing a compressed air current directed against the yarn withdrawal direction is connected to a compressed air source. In a simple fashion, the yarn withdrawal pipe also serves as the compressed air nozzle which carries out the return transport of the yarn end within the spinning unit via the yarn formation zone. It is advantageously contemplated that the yarn withdrawal pipe of each spinning unit be provided with a channel entering the unit in a sloped orientation against the yarn withdrawal direction, serving as a compressed air supply line which leads to a compressed air source. An air current is thereby produced within the yarn withdrawal pipe of the kind known with ejector pumps which may also be used for taking in the yarn end presented in the area of the outlet of the yarn withdrawal pipe. In addition, the yarn withdrawal pipe then also serves as a compressed air nozzle. Since there exists a transport air current produced by a compressed air source within the yarn withdrawal pipe, the same may exhibit any desired path and especially may include one or several deflections of the yarn path without disturbing the return transport of the yarn end.
In a further development of certain preferred embodiments of the invention the maintenance device includes a compressed air supply line attachable to the compressed air nozzle of a spinning unit requiring service. The compressed air nozzle which, for example, could be the yarn withdrawal pipe, is stationarily attached to each spinning unit and directed to the yarn formation zone. The supply line of the movable maintenance device need only be attached, without the movable maintenance device having to adjust the air nozzle in relation to the yarn formation zone of the spinning unit.
With another preferred embodiment of the invention, a compressed air nozzle connected to a compressed air supply line is included in the maintenance device that is attachable to a spinning unit requiring service.
In another preferred embodiment of the invention it is provided that the means for producing an air current in the area of the yarn formation zone directed against the normal yarn withdrawal direction include a suction nozzle controllable by the maintenance device. As a result, the yarn end is returned, and upon entering the suction nozzle, takes on a precisely defined position in the spinning unit.
In a further development of certain preferred embodiments of the invention the maintenance device is equipped with a device for detecting the yarn end drawn in by the suction nozzle. The maintenance device is thereby given the opportunity to examine whether the yarn end has been returned and whether, as a result thereof, the requirements for a successful piecing process are met.
In another development of certain preferred embodiments of the invention, the maintenance device is equipped with means for piecing and/or treating of the yarn end to be drawn in by the suction nozzle. These measures make it possible to piece the returned yarn end to an exact length and to treat same, if necessary, upon its return so that the prerequisite for a successful piecing process are further improved.
In a further development of certain preferred embodiments of the invention, each spinning unit is equipped with means for interrupting a drive unit of the friction surface means forming the yarn formation zone, and the maintenance device includes control means for controlling the means for interrupting the drive unit. As a consequence, the movable maintenance device is capable of disengaging the drive of the friction surface means defining the yarn formation zone, thereby avoiding any disturbance by the friction surface means during the return of the yarn end.
In a further development of the invention each spinning unit is equipped with means for interrupting the suction effect of the suction device attached to the respective yarn formation zone, and the maintenance device includes means for controlling the means for interrupting the suction effect. Furthermore, by providing that the maintenance device is capable of interrupting the suction effect, any negative influence of the suction effect in the area of the yarn formation zone during the return of the yarn end is avoided.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.